alright so my 93 sol si is getting 22 hiway i had my brother run it on the scan system and everything checked out perfect. plugs are white, brown color. i have no clue why my car is doing thins. any guesses?

Could be so many things. Post up a pic of the plugs if ya can, also give us some more info like, which engine, how many miles, service schedule, any Mods you've made to the engine, any other issues that you may have had or noticed, does it have any other symptoms, (smoking, running rough, sputtering)???

Have you checked the timing, checked the injectors, changed the fuel filter, tires good? And is this a new event that changed out of the blue or has it been this way since you've had the car, and if all of the sudden then what was the last changes that you made??? What kind of driving (city- hwy) and is this your DD?

I'm not a guru on this subject but I bet more info could help to resolve the problem...

1.6 d16z6 dd my brother is a tech and makes sure every little detail is perfect. everything is up to date on the car. it was getting 38-40 hw and just randomly dropped to 22ish i have no upgrades to the car. all stock. little black buildup on the rear bumper from the exhaust, not burning oil tho. it is an automatic too. i am frigen pissed, it cost me 80$ a week to drive 60 miles every day. when i was getting about 400 miles to a tank. i cant afford gas to get to school now i dont have a job anymore...... just frigen stressed. like i said absolutly everything checks out ok in the system.

Even though its testing good O2 might be starting to fail and might be enriching the fuel. The black soot is a good sign of running rich. Could also have a dirty injector thats not closing all the way and still spraying a little extra.